Alpha
Decay (α Decay) : The phenomenon of emission of α-particle
from a radioactive nucleus is called α Decay.

Atmosphere
: The gaseous envelope around the earth is called atmosphere.

Atomic
Nucleus : The central core of the atom which contains
all of the atom's positive charge and most of its mass is
known as atomic nucleus.

Atomic
Number : The number of protons in a nucleus (or nuclide)
is called the atomic number and is represented by the symbol
Z. In a natural atom, the number of electrons obtain the nucleus
is equal to the atomic number Z.

Activity
: The rate of disintegration (i.e. number of disintegrations
per second) in a radioactive substance is known as its activity
i.e. Activity of a radioactive substance, A = - dN / dt.

Artificial
Radioactivity : The phenomenon of making a stable nucleus
radioactive by artificial means is known as artificial radioactivity.

Analog
Signal : A continuously varying signal (voltage or current)
is called an analog signal.

AND
Gate :The AND gate
is a logic gate that has two or more inputs but only one output.
However, the output Y of an AND gates is HIGH when all inputs
are HIGH. The output Y of an AND gate is LOW if any or all
the inputs are LOW.

Attenuation
: The loss of strength of the signal while propagating
through the medium is known as attenuation.

Amplification
: The process of raising the strength of a signal is called
amplification and is done by an electronic circuit called
amplifier.

Antenna
: An antenna or aerial is a system of elevated conductors
which couples the transmitter or the receiver to free space.

Amplitude
Modulation (AM) : When the amplitude of high frequency
carrier wave is changed in accordance with the intensity of
the signal, it is called amplitude modulation (AM).